Linear solenoids are constructed of an armature disposed within a conductive coil. When electricity is applied to the conductive coil, a magnetic field is created resulting in a force on a ferromagnetic armature causing a displacement of the armature along the axis of the coil. The displacement, in turn, causes a shaft connected to the armature to also shift along the axis. In some cases, such as those where the linear solenoid is subjected to vibrations, or is angled relative to a force of gravity, the armature can contact the interior surface of the coils. The contact between the armature and the coils can result in fretting wear and/or galling. The wear, in turn, can cause degradation in the performance of the linear solenoid, and can increase the amount of electrical energy required to allow the linear solenoid to function.
One solution that has been attempted in the art is disposing guide rings in a circumferential groove around the armature and between the interior surface of the coil and the exterior surface of the armature. However, sizing the guide rings can be difficult and an improper sizing can result in further fretting wear, the creation of debris, or armature to bore contact. Further, placing the guide rings in a circumferential groove allows the armature to move axially within the gap between the guide ring and groove and provides little resistance to armature rotation. As used herein, the bore refers to the radially interior surface of the coil component. Further, in some examples, the guide rings can cause the armature to rotate within the coils when exposed to vibrations and the rotation can further increase fretting wear.
Additionally, guide rings can form a seal around the armature which allows for a delta pressure to act on the armatures area, slowing the reaction time of the armature. The reduced reaction time is typically mitigated by drilling a hole in the armature to allow pressure to equalize. However, drilling a hole in the armature can affect the magnetic force or create a gap in the guide ring.